Hydrocarbon feedstock containing higher molecular weight hydrocarbons is cracked by contacting it under elevated temperatures with a cracking catalyst whereby light distillates are produced. However, the cracking catalyst gradually deteriorates during this process. One source for this deterioration is the deposition of metals, such as nickel, vanadium and iron, on the catalyst which increase the production of hydrogen, dry gas and coke. At the same time the conversion of the hydrocarbons into gasoline is reduced.